1. Field of the Invention
The present invention relates to transformer coils, and particularly relates to transformer coils including at least two windings wrapped around a coil shaft.
2. Description of the Related Art
The transformer coil disclosed in Japanese Unexamined Patent Application Publication No. 8-162336, for example, is known as a conventional transformer coil. FIG. 8 is a plan view of a transformer coil 500 disclosed in Japanese Unexamined Patent Application Publication No. 8-162336.
The transformer coil 500 includes a coil bobbin 502, a pin terminal 510, and a winding 520. The coil bobbin 502 is configured of a core 504, an upper flange 506, and a lower flange 508. The core 504 extends in a vertical direction. The upper flange 506 is connected to an upper end of the core 504. The lower flange 508 is connected to a lower end of the core 504.
In addition, a groove 512 that extends in the vertical direction is provided in a side surface of the lower flange 508. The pin terminal 510 protrudes downward from a bottom surface of the lower flange 508.
The winding 520 is wrapped around the core 504. Furthermore, the winding 520 is guided by the groove 512 and is drawn out from the bottom surface of the lower flange 508. Both ends of the winding 520 are wrapped around the pin terminal 510.
In the transformer coil 500 disclosed in Japanese Unexamined Patent Application Publication No. 8-162336, the winding 520 is covered by an insulative material. Accordingly, to connect the winding 520 and the pin terminal 510, the winding 520 is wrapped around the pin terminal 510 and is dipped in a solder liquid. At this time, the liquid surface of the solder liquid is located at a base of the pin terminal 510 (that is, at a location L0). The covering of the winding 520 is thus melted by heat from the solder liquid. As a result, the winding 520 and the pin terminal 510 are connected by the solder.
Incidentally, the solder liquid wets upward along the winding 520. There is thus a risk that the cover of the winding 520 located within the groove 512 will also be melted. Accordingly, in the transformer coil 500 disclosed in Japanese Unexamined Patent Application Publication No. 8-162336, a width of an upper portion of the groove 512 is smaller than a width of a lower portion of the groove 512. The solder liquid is suppressed from wetting upward within the groove 512 as a result.
However, with the transformer coil 500 disclosed in Japanese Unexamined Patent Application Publication No. 8-162336, there is a risk that the cover of the winding 520 located within the groove 512 will melt due to heat transmitted from the solder liquid to the winding 520.